The invention relates to a magnetic device comprising at least one thin magnetic domain layer of a magnetizable material which has an easy axis of magnetization which is substantially normal to the surface of the layer, which layer has a pattern of electrically conductive material and elements which cause an asymmetry force, and furthermore comprising bipolar current-supplying means for propagating magnetic domains in the layer in cooperation with the pattern of electrically conductive material.
In such a device which is known from Journal of Applied Physics, Vol. 42, No. 4, Mar. 15, 1971, pp. 1266-1267, the thin layer of magnetizable material has a pattern of electrically conductive material in a first configuration. The elements which cause an asymmetry force which is necessary to determine the direction in which the magnetic domains propagate are formed by a pattern of dots of soft-magnetic material in a second configuration. If such elements which cause an asymmetry force were not present, then it would be possible to propagate the magnetic domains under the influence of a bipolar current, for example an alternating current, from a first to a second position, but it could not be determined beforehand which second position that is. In other words, the direction in which the propagation occurs would then be indefinite.
During the manufacture of the device, two patterns are provided one after the other by means of mask technology, the critical dimension being the radius of the magnetic domains. This requires that in order to provide the second pattern, the relevant mask has to be aligned very accurately with respect to the first pattern. As a result of this, size restrictions arise, in particular relating to the dimensions of the magnetic domains. These restrictions also occur in other known embodiments of the elements which cause an asymmetry force, for example, a second pattern of electrically conductive material over the first pattern of the same configuration but shifted over a small distance relative thereto, or a groove of variable width etched in the thin layer of magnetizable material.